The present invention relates generally to an apparatus and method for tuning a rotational speed of vacuum pump using an automated control scheme.
A vacuum pump is a device for evacuating gas from an enclosed space in order to create a low pressure environment within the space. It is often used in a semiconductor manufacturing process. For example, one or more vacuum pumps can be used to evacuate the gas in a process chamber during a chemical vapor deposition (CVD) process. As another example, the vacuum pump can be used to create a low pressure environment in a load lock chamber interfacing between a process chamber and ambient environment. Examples of vacuum pumps categorized by their functions in a semiconductor manufacturing process include, without limitation, booster pumps, load lock pumps, and backing pumps.
Conventionally, a vacuum pump is often over specified to accommodate many variables for different applications, in order to provide a certain assurance of performance. Semiconductor fabrication plants have various pipe work geometries and manufacturing equipment tolerances. An over-specified vacuum pump can easily accommodate different installation requirements in various semiconductor fabrication plants, and still guarantee certain satisfaction of minimum performance.
Although over-specification enables vacuum pumps to accommodate various installation requirements, it has the drawback of inefficiency in energy consumption. An over-specified vacuum pump tends to operate at a rotational speed higher than an optimal level. As a result, it tends to consume more energy than what is needed for an acceptable performance.
Conventionally, manual adjustment of pump speed during operation has been attempted in order to conserve energy. However, such method is crude and inaccurate. It may not be able to provide the accuracy level needed for a vacuum pump to operate at an optimal speed. Furthermore, manual adjustment is inconsistent and prone to errors. This may cause undesired process variations.